Algae, slime and bacteria concentrations often plague water storage or supply systems such as sewage systems, cooling tower complexes, potable water supplies, systems for fire prevention, irrigation, etc. Ocean water storage or supply systems will foul with algae, slime and numerous additional organisms such as barnacles, tunicates, hydroids, bryozoa and others. The proliferation of these organisms is prevented by the application of chlorine. Chlorine gas, although economical, is risky to store and use. Anhydrous liquid chlorine is also risky to store and to use and has a high thermal coefficient of expansion so that even moderate elevation in temperature could cause hydrostatic rupture of a container tank.
Sodium hypochlorite is the alternative form of chlorine that comes closest to being economically feasible as a chlorinating agent. Although the relative safety of sodium hypochlorite is well known, it still presents storage problems because of the large quantities that must be used. A solution to the storage and safety problem is to provide a system that can produce sodium hypochlorite as needed with no storage required.
In copending U.S. patent application Ser. No. 357,555 filed May 7, 1973, assigned to the assignee of this application, there is disclosed a generator for the production of sodium hypochlorite on demand in whatever quantities are required. In that application a sodium hypochlorite generator is disclosed in which there are inner and outer cylindrical members defining an annular space through which electrolyte flows. One of the cylindrical members is formed of two parts, one being an anode and the other a cathode insulated from each other, and the other cylindrical member forms a bipolar element operating in conjunction with the anode and cathode of the first cylindrical member. In one embodiment shown in that application, the bipolar cylindrical element is the outer cylindrical member, and in the second and preferred embodiment the bipolar element is the inner cylindrical member.
The improvement of this invention may be used with either of those embodiments. Reference herein in the specification or claims to a "cell" or "cell assembly" means a hypochlorite generating cell assembly of the type disclosed in that copending application.